English
There exists a canonical measurable equivalence FinTwoArrow between a product of two copies of a space and their product, preserving the product measure structure.
Русский
Существует каноническое измеримое эквивалентное отображение FinTwoArrow между произведением двух копий пространства и их произведением, сохраняющее меру.
LaTeX
$$$ \mathrm{MeasurePreserving}\bigl(\mathrm{MeasurableEquiv.finTwoArrow}(\alpha)\bigr)\; (\mathrm{Measure.pi}\; (λ i. μ))\; (μ.prod μ) $$$
Lean4
theorem measurePreserving_finTwoArrow {α : Type u} {m : MeasurableSpace α} (μ : Measure α) [SigmaFinite μ] :
MeasurePreserving MeasurableEquiv.finTwoArrow (Measure.pi fun _ => μ) (μ.prod μ) := by
simpa only [Matrix.vec_single_eq_const, Matrix.vecCons_const] using measurePreserving_finTwoArrow_vec μ μ